1. Field of the Invention
The present invention relates to a caliper and a caliper grip. More specifically, it relates to a caliper having a grip movable relative to a main scale and a caliper grip.
2. Description of Related Art
Vernier scale caliper having a main scale provided with main scale graduations formed along the longitudinal direction of the main scale and a slider with vernier graduations formed thereon, a dial display caliper that converts a movement of a slider into rotation of a dial pointer, and a digital display caliper that converts a movement of the slider into an electric signal by a photoelectric, an electrostatic or a magnetic encoder and digitally displays the movement in accordance with the signal on a digital display are conventionally known.
In measuring with such conventional calipers, workpiece is grabbed by one hand and a main scale is grasped with the other hand, where a slider is moved along the main scale while applying thumb of the other hand to the slider to bring an inner or outer jaw provided to the main scale and the slider into contact with the target portions of the workpiece. The dimension of the workpiece etc. can be obtained from the main scale graduation and vernier graduation (in vernier scale caliper), dial pointer (in dial display caliper) or indication on the digital display (in digital display caliper).
However, since the slider has to be moved while grasping the main scale with one hand during measurement, following disadvantages occurred in the conventional calipers.
(a) Since the main scale has rectangular cross section in order to allow the movement of the slider, it is difficult to hold the main scale with the one hand. Especially, when the workpiece is to be measured while moving the slider is moved to a point around effective measurement range relative to the main scale, little space is left on the main scale to be held. For instance, when a caliper having effective measurement range of 10 cm is used to measure a dimension around 10 cm, since the slider is moved to a position near a distal end of the main scale, little space is left on the main scale to be grasped.
(b) Further, since the measurement is conducted while directly holding the main scale with one hand, the heat of the hand is transferred to the main scale, which can influence on measurement result. Especially, since electrode is buried along the longitudinal direction of the main scale in a digital display caliper, the heat of the hand can influence on the measurement accuracy.
(c) The worker may sometimes hold the main scale with hand adhered with oil in a factory. In such environment, the graduation of vernier scale caliper may get dirty by oil etc., so that legibility is deteriorated. Further, when a worker conducts measurement while holding the main scale with hand adhered with chip etc., the chip may damage the electrode of digital display caliper.
Accordingly, the applicant of the present application has proposed a caliper for overcoming the above disadvantages (see U.S. Pat. No. 5,483,751), in which a tube-shaped synthetic-resin cover covering the main scale is attached to the slider.
According to the above arrangement, the synthetic-resin cover is held with one hand and the slider is moved along the longitudinal direction of the main scale while applying the finger cushion of the thumb of the hand to a press roller attached to the slider, thereby bringing the measuring jaw into contact with a target portion of a workpiece.
Accordingly, since measurement can be conducted while holding the tube-shaped cover having a design enabling easy holding without holding the main scale, the above disadvantage of difficulty in holding the rectangular-cross-sectional main scale can be avoided. There is no problem of little space for holding the main scale in measuring a dimension around the effective measurement range. Further, since synthetic resin of low thermal conductivity is used for the tube-shaped cover, the heat is hardly transferred to the main scale. Since the cover is held without directly holding the main scale, the contamination by oil and chip adhered on hand can be avoided.
However, since the slider has to be specially machined in attaching the cover to the slider in the conventional caliper (U.S. Pat. No. 5,483,751), troublesome work and considerable production cost are necessary therefor.
An object of the present invention is to provide a caliper and a caliper grip capable of eliminating the above conventional disadvantages, superior in operability and readability, with the measurement accuracy thereof being hardly influenced by heat from hand and superior in processing work and production cost.
In order to achieve the above object, the caliper and caliper grip of the present invention has the following arrangement.
A caliper according to an aspect of the present invention has: a main scale having a first measuring jaw; a slider movable along a longitudinal direction of the main scale and having a second measuring jaw to be in contact with a workpiece together with the first measuring jaw; and a tube-shaped grip provided on a side of the main scale opposite to the measuring jaws relative to the slider, the grip covering the main scale and being movable in the longitudinal direction of the main scale.
According to the above arrangement, after displacing the grip to a position capable of measuring a dimension slightly greater than a target portion, the grip is held with one hand and the slider is moved while pushing the slider with the thumb of the one hand. While the measuring jaw of the slider and the measuring jaw of the main scale are in contact with the workpiece by moving the slider, the dimension between the measuring jaws, i.e. the dimension of the workpiece, is read. The dimension of the workpiece is read by a main graduation of the main scale and a vernier graduation of the slider, the graduation coincident with the pointer of a dial of a dial display caliper and a numeral on a digital display of a dial display caliper.
Accordingly, since the slider can be manipulated while holding the grip, difficulty in holding the rectangular-cross-sectional main scale and the problem of little holding space on the main scale when the slider is moved relative to the main scale to a point around the effective measurement range can be resolved. Since the heat is not directly transferred to the main scale by holding the grip with hand, deterioration of dimension accuracy by heat can be reduced. Since it is not necessary to hold the main scale directly with one hand, difficulty in reading the graduation of the vernier scale caliper caused by holding the main scale with oil-stained hand and damage on the electrode caused by chips adhered on hand can be prevented. Since the grip is not necessary to be connected to the slider, no work and processing for connecting the grip to the slider is required, thus reducing cost therefor.
In the above caliper, a plate spring slidable relative to the main scale when the grip is moved in the longitudinal direction of the main scale may preferably be provided on an inner wall of the grip.
According to the above arrangement, since the spring force can be changed by adjusting shape and material of the spring portion of the plate spring, the grip can be adjusted to be stilled in measuring dimension and moved with relatively low force during movement.
In the caliper according to the above aspect of the present invention, a rib slidable relative to the main scale when the grip is moved in the longitudinal direction of the main scale may preferably be provided on an inner wall of the grip.
According to the above arrangement, since the pressing force of the grip toward the main scale can be changed in accordance with the size and shape of the rib, the grip can be adjusted to be stilled in measuring dimension and moved with relatively low force during movement.
In the caliper according to the above aspect of the present invention, a slide member independent of the grip may preferably be provided between the grip and the main scale.
According to the above arrangement, since original slide condition can be recovered by exchanging the slide member as one of the components of the grip when the slide member is worn down, the cost can be reduced as compared to an arrangement for exchanging the entire grip.
In the caliper according to the above aspect of the present invention, the grip may preferably include a grip body covering at least a part of the main scale and a movable member turnably supported by the grip body through a turn shaft and having an end adapted to be in contact with the main scale, and a biasing means for biasing the movable member in a direction for the end of the movable member to be in contact with the main scale.
According to the above arrangement, in moving the grip, the movable member is turned in a direction for an end of the movable member to be away from the main scale against the biasing means and the grip is moved in the longitudinal direction of the main scale. Since the grip is moved while the movable member is out of contact with the main scale, no abrasion is caused by slide movement and the grip can be moved with low force. When the movable member is turned by the biasing means at a desired position, an end of the movable member is in contact with the main scale and the grip is stilled at the position. The slider can be moved by holding the grip at the position. Even when the grip has been assembled, the main scale can be inserted between the grip body and the movable member by turning the movable member against the biasing means in a direction for an end to move away from the main scale, so that the grip can be easily attached to various existing calipers only by turning the movable member at a desired position by the biasing means and the grip can be detached from the caliper only by turning the movable member against the biasing means.
In the caliper according to the above aspect of the present invention, a pair of holding portions for holding the main scale and slidable relative to the main scale may preferably be formed inside the grip, a first grip component including a first holding portion of the pair of holding portions may preferably be displaceable relative to a second grip component including a second holding portion of the pair of holding portions in a direction for the first holding portion to move away from the second holding portion, and a fitting for mutually engaging the first grip component and the second grip component when the main scale is held by the pair of holding portions may preferably be provided.
According to the above arrangement, since the gap between the pair of holding portions is enlarged by displacing the first grip component in a direction for widening the gap between the holding portions, the main scale can be inserted into the gap. After the first grip component is displaced to the second grip component in a direction for the gap between the holding portions to return to original condition, both of the grip components are mutually engaged by the fitting. Then, the pair of holding portions hold the main scale, so that the grip can be stilled at any position relative to the main scale of the caliper and can be moved with a relatively low force during movement.
Accordingly, the grip can be attached and detached to existing calipers without special processing and the grip can be stilled at any position relative to the main scale of the caliper and can be moved with a relatively low force during movement.
A caliper grip according to another aspect of the present invention is used for a caliper including a main scale having a first measuring jaw and a slider movable along a longitudinal direction of the main scale having a second measuring jaw to be in contact with a workpiece together with the first measuring jaw, in which the caliper grip is movable on the main scale and stoppable at a desired position on the main scale, the caliper grip being formed in a tube-shape covering the main scale.
According to the above arrangement, the same function and advantages as the caliper of the present invention can be obtained.
In the above, a pair of holding portions for holding the main scale and slidable relative to the main scale may preferably be formed inside the grip, a first grip component including a first holding portion of the pair of holding portions may preferably be displaceable relative to a second grip component including a second holding portion of the holding portions in a direction for the first holding portion to move away from the second holding portion, and a fitting for mutually engaging the first grip component and the second grip component when the main scale is held by the pair of holding portions may preferably be provided.
According to the above arrangement, the grip can be attached and detached to existing calipers without special processing and the grip can be stilled at any position relative to the main scale of the caliper and can be moved with a relatively low force during movement.